EUCAST Technical Note on Aspergillus and amphotericin B, itraconazole, and posaconazole

Comparison of EUCAST and CLSI Reference Microdilution MICs of Eight Antifungal Compounds for Candida auris and Associated Tentative Epidemiological Cutoff Values

Candida auris is an emerging multidrug-resistant yeast. So far, all but two susceptibility testing studies have examined ≤50 isolates, mostly with the CLSI method. We investigated CLSI and EUCAST MICs for 123 C. auris isolates and eight antifungals and evaluated various methods for epidemiological cutoff (ECOFF) determinations. MICs (in milligrams per liter) were determined using CLSI method M27-A3, and the EUCAST E.Def 7.3. ANOVA analysis of variance with Bonferroni's multiple-comparison test and Pearson analysis were used on log₂ MICs (significance at P values of <0.05). The percent agreement (within ±0 to ±2 2-fold dilutions) between the methods was calculated. ECOFFs were determined visually, statistically (using the ECOFF Finder program and MicDat1.23 software with 95% to 99% endpoints), and via the derivatization method (dECOFFs). The CLSI and EUCAST MIC distributions were wide, with several peaks for all compounds except amphotericin B, suggesting possible acquired resistance. Modal MIC, geometric MIC, MIC₅₀, and MIC₉₀ values were ≤1 2-fold dilutions apart, and no significant differences were found. The quantitative agreement was best for amphotericin B (80%/97% within ±1/±2 dilutions) and lowest for isavuconazole and anidulafungin (58%/76% to 75% within ±1/±2 dilutions). We found that 90.2%/100% of the isolates were amphotericin B susceptible based on CLSI/EUCAST methods, respectively (i.e., with MICs of ≤1 mg/liter), and 100%/97.6% were fluconazole nonsusceptible by CLSI/EUCAST (MICs > 2). The ECOFFs (in milligrams per liter) were similar across the three different methods for itraconazole (ranges for CLSI/EUCAST, 0.25 to 0.5/0.5 to 1), posaconazole (0.125/0.125 to 0.25), amphotericin B (0.25 to 0.5/1 to 2), micafungin (0.25 to 0.5), and anidulafungin (0.25 to 0.5/0.25 to 1). In contrast, the estimated ECOFFs were dependent on the method applied for voriconazole (1 to 32) and isavuconazole (0.125 to 4). CLSI and EUCAST MICs were remarkably similar and confirmed uniform fluconazole resistance and variable acquired resistance to the other agents.

In Vivo Efficacy of Liposomal Amphotericin B against Wild-Type and Azole-Resistant Aspergillus fumigatus Isolates in Two Different Immunosuppression Models of Invasive Aspergillosis

Using an immunocompetent murine model of invasive aspergillosis (IA), we previously reported that the efficacy of liposomal amphotericin B (L-AmB) (Ambisome) is not hampered by the presence of azole resistance mutations in Aspergillus fumigatus (S. Seyedmousavi, W. J. G. Melchers, J. W. Mouton, and P. E. Verweij, Antimicrob Agents Chemother 57:1866-1871, 2013, https://doi.org/10.1128/AAC.02226-12). We here investigated the role of immune suppression, i.e., neutropenia and steroid treatment, in L-AmB efficacy in mice infected with wild-type (WT) A. fumigatus and with azole-resistant A. fumigatus harboring a TR₃₄/L98H mutation in the cyp-51A gene. Survival of treated animals at day 14 in both immunosuppressed models was significantly better than that of nontreated controls. A dose-response relationship was observed that was independent of the azole-resistant mechanism and the immunosuppression method used. In the neutropenic model, 100% survival was reached at an L-AmB dose of 16 mg/kg of body weight for the WT strain and the TR₃₄/L98H isolate. In the steroid-treated group, 90.9% survival and 100% survival were achieved for the WT isolate and the TR₃₄/L98H isolate with an L-AmB dose of 16 mg/kg, respectively. The 50% effective dose (ED₅₀) was 1.40 mg/kg (95% confidence interval [CI], 0.66 to 3.00 mg/kg) for the WT isolate and 1.92 mg/kg (95% CI, 0.60 to 6.17 mg/kg) for the TR₃₄/L98H isolate in the neutropenic model and was 2.40 mg/kg (95% CI, 1.93 to 2.97 mg/kg) for the WT isolate and 2.56 mg/kg (95% CI, 1.43 to 4.56 mg/kg) for the TR₃₄/L98H isolate in the steroid-treated group. Overall, there were no significant differences between the two different immunosuppressed conditions in the efficacy of L-AmB against the wild-type and azole-resistant isolates (P > 0.9). However, the required L-AmB exposure was significantly higher than that seen in the immunocompetent model.

Triazole Resistance in Aspergillus fumigatus Clinical Isolates Obtained in Nanjing, China

BACKGROUND

During the past decades, the incidence of invasive aspergillosis (IA) caused by Aspergillus fumigatus has increased dramatically. The aims of this study were to investigate the susceptibility of clinical isolates of A. fumigatus to triazole and the underlying cyp51A mutations in triazole-resistant A. fumigatus.

METHODS

A total of 126 A. fumigatus clinical isolates from 126 patients with proven or probable IA were obtained from four large tertiary hospitals in Nanjing, China, between August 2012 and July 2015. The determination of minimal inhibitory concentrations (MICs) for itraconazole, voriconazole, and posaconazole was performed by broth microdilution according to the European Committee on Antimicrobial Susceptibility Testing reference method.

RESULTS

A total of 4 A. fumigatus isolates (3.17%) were confirmed to be itraconazole resistant, with MICs of ≥8 mg/L, and one isolate (0.8%) was confirmed to be voriconazole resistant and posaconazole resistant, with MICs of 4 mg/L and 0.5 mg/L, respectively. We found that two of the 4 isolates of triazole-resistant A. fumigatus had the L98H amino acid substitution in combination with a 34-base pair tandem repeat in the promoter region, one isolate had an M220I mutation, and another itraconazole-resistant isolate did not have a substitution in the cyp51A gene.

CONCLUSIONS

This study shows that triazole-resistant A. fumigatus clinical isolates are present in Nanjing, China, which is a new challenge to the clinical management of IA.

Genetic Diversity and In Vitro Antifungal Susceptibility of 200 Clinical and Environmental Aspergillus flavus Isolates

Aspergillus flavus has been frequently reported as the leading cause of invasive aspergillosis in certain tropical and subtropical countries. Two hundred A. flavus strains originating from clinical and environmental sources and collected between 2008 and 2015 were phylogenetically identified at the species level by analyzing partial β-tubulin and calmodulin genes. In vitro antifungal susceptibility testing was performed against antifungals using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) broth microdilution method. In addition, genotyping was performed using a short-tandem-repeat (STR) assay of a panel of six microsatellite markers (A. flavus 2A, 2B, 2C, 3A, 3B, and 3C), in order to determine the genetic variation and the potential relationship between clinical and environmental isolates. The geometric means of the minimum inhibitory concentrations/minimum effective concentrations (MICs/MECs) of the antifungals across all isolates were (in increasing order): posaconazole, 0.13 mg/liter; anidulafungin, 0.16 mg/liter; itraconazole, 0.29 mg/liter; caspofungin, 0.42 mg/liter; voriconazole, 0.64 mg/liter; isavuconazole, 1.10 mg/liter; amphotericin B, 3.35 mg/liter; and flucytosine, 62.97 mg/liter. All of the clinical isolates were genetically different. However, an identical microsatellite genotype was found between a clinical isolate and two environmental strains. In conclusion, posaconazole and anidulafungin showed the greatest in vitro activity among systemic azoles and echinocandins, respectively. However, the majority of the A. flavus isolates showed reduced susceptibility to amphotericin B. Antifungal susceptibility of A. flavus was not linked with the clinical or environmental source of isolation. Microsatellite genotyping may suggest an association between clinical and environmental strains, although this requires further investigation.

A prospective international Aspergillus terreus survey: an EFISG, ISHAM and ECMM joint study

OBJECTIVES

A prospective international multicentre surveillance study was conducted to investigate the prevalence and amphotericin B susceptibility of Aspergillus terreus species complex infections.

METHODS

A total of 370 cases from 21 countries were evaluated.

RESULTS

The overall prevalence of A. terreus species complex among the investigated patients with mould-positive cultures was 5.2% (370/7116). Amphotericin B MICs ranged from 0.125 to 32 mg/L, (median 8 mg/L).

CONCLUSIONS

Aspergillus terreus species complex infections cause a wide spectrum of aspergillosis and the majority of cryptic species display high amphotericin B MICs.

Rifampin Enhances the Activity of Amphotericin B against Fusarium solani Species Complex and Aspergillus flavus Species Complex Isolates from Keratitis Patients

The in vitro activities of amphotericin B in combination with rifampin were assessed against 95 ocular fungal isolates. The interactions between amphotericin B and rifampin at 4, 8, 16, and 32 μg/ml were synergistic for 11.8%, 51.0%, 90.2%, and 94.1%, respectively, of Fusarium solani species complex isolates and for 13.6%, 45.5%, 93.2%, and 95.5%, respectively, of Aspergillus flavus species complex isolates. Antagonism was never observed for the amphotericin B-rifampin combinations.

Molecular identification and amphotericin B susceptibility testing of clinical isolates of Aspergillus from 11 hospitals in Korea

BACKGROUND

We investigated the species distribution and amphotericin B (AMB) susceptibility of Korean clinical Aspergillus isolates by using two Etests and the CLSI broth microdilution method.

METHODS

A total of 136 Aspergillus isolates obtained from 11 university hospitals were identified by sequencing the internal transcribed spacer (ITS) and β-tubulin genomic regions. Minimal inhibitory concentrations (MICs) of AMB were determined in Etests using Mueller-Hinton agar (Etest-MH) and RPMI agar (Etest-RPG), and categorical agreement with the CLSI method was assessed by using epidemiological cutoff values.

RESULTS

ITS sequencing identified the following six Aspergillus species complexes: Aspergillus fumigatus (42.6% of the isolates), A. niger (23.5%), A. flavus (17.6%), A. terreus (11.0%), A. versicolor (4.4%), and A. ustus (0.7%). Cryptic species identifiable by β-tubulin sequencing accounted for 25.7% (35/136) of the isolates. Of all 136 isolates, 36 (26.5%) had AMB MICs of ≥2 μg/mL by the CLSI method. The categorical agreement of Etest-RPG with the CLSI method was 98% for the A. fumigatus, A. niger, and A. versicolor complexes, 87% for the A. terreus complex, and 37.5% for the A. flavus complex. That of Etest-MH was ≤75% for the A. niger, A. flavus, A. terreus, and A. versicolor complexes but was higher for the A. fumigatus complex (98.3%).

CONCLUSIONS

Aspergillus species other than A. fumigatus constitute about 60% of clinical Aspergillus isolates, and reduced AMB susceptibility is common among clinical isolates of Aspergillus in Korea. Molecular identification and AMB susceptibility testing by Etest-RPG may be useful for characterizing Aspergillus isolates of clinical relevance.

Antifungal pharmacodynamics: Latin America's perspective

The current increment of invasive fungal infections and the availability of new broad-spectrum antifungal agents has increased the use of these agents by non-expert practitioners, without an impact on mortality. To improve efficacy while minimizing prescription errors and to reduce the high monetary cost to the health systems, the principles of pharmacokinetics (PK) and pharmacodynamics (PD) are necessary. A systematic review of the PD of antifungals agents was performed aiming at the practicing physician without expertise in this field. The initial section of this review focuses on the general concepts of antimicrobial PD. In vitro studies, fungal susceptibility and antifungal serum concentrations are related with different doses and dosing schedules, determining the PD indices and the magnitude required to obtain a specific outcome. Herein the PD of the most used antifungal drug classes in Latin America (polyenes, azoles, and echinocandins) is discussed.

A prospective study of treatment of carbapenem-resistant Enterobacteriaceae infections and risk factors associated with outcome

BACKGROUND

To describe the clinical and microbiological data of carbapenem-resistant Enterobacteriaceae (CRE) infections, the treatment used, hospital- and infection-related mortality, and risk factors for death.

METHODS

A prospective cohort conducted from March 2011 to December 2012. Clinical, demographic, and microbiological data such as in vitro sensitivity, clonality, carbapenemase gene mortality related to infection, and overall mortality were evaluated. Data were analyzed using Epi Info version 7.0 (CDC, Atlanta, GA, USA) and SPSS (Chicago, IL, USA).

RESULTS

One hundred and twenty-seven patients were evaluated. Pneumonia, 52 (42 %), and urinary tract infections (UTI), 51 (40.2 %), were the most frequent sites of infection. The isolates were polyclonal; the Bla KPC gene was found in 75.6 % of isolates, and 27 % of isolates were resistant to colistin. Mortality related to infection was 34.6 %, and was higher among patients with pneumonia (61.4 %). Combination therapy was used in 98 (77.2 %), and monotherapy in 22.8 %; 96.5 % of them were UTI patients. Shock, age, and dialysis were independent risk factors for death. There was no difference in infection-related death comparing colistin-susceptible and colistin-resistant infections (p = 0.46); neither in survival rate comparing the use of combination therapy with two drugs or more than two drugs (p = 0.32).

CONCLUSIONS

CRE infection mortality was higher among patients with pneumonia. Infections caused by colistin-resistant isolates did not increase mortality. The use of more than two drugs on combination therapy did not show a protective effect on outcome. The isolates were polyclonal, and the bla KPC gene was the only carbapenemase found. Shock, dialysis, and age over 60 years were independent risk factors for death.

Blood and tissue distribution of posaconazole in a rat model of invasive pulmonary aspergillosis

Posaconazole is the recommended prophylactic agent in patients at high risk of invasive fungal infection, since adequate drug levels seem to be reached in target sites despite the relatively low levels detected in blood. The objective of this study is to obtain pharmacokinetic (PK) information associated to blood and tissue distribution of posaconazole in an animal model of invasive pulmonary aspergillosis. The PK parameters in lung samples were systematically higher than in serum. After multiple-dose administration of posaconazole, a significant accumulation of the drug was evident in lung tissue. The PK behavior of posaconazole in this particular experimental model is similar to that observed in humans. Thus, we believe this model could be a valid tool to evaluate posaconazole exposure-response relationship.

Sterol Biosynthesis and Azole Tolerance Is Governed by the Opposing Actions of SrbA and the CCAAT Binding Complex

Azole drugs selectively target fungal sterol biosynthesis and are critical to our antifungal therapeutic arsenal. However, resistance to this class of drugs, particularly in the major human mould pathogen Aspergillus fumigatus, is emerging and reaching levels that have prompted some to suggest that there is a realistic probability that they will be lost for clinical use. The dominating class of pan-azole resistant isolates is characterized by the presence of a tandem repeat of at least 34 bases (TR34) within the promoter of cyp51A, the gene encoding the azole drug target sterol C14-demethylase. Here we demonstrate that the repeat sequence in TR34 is bound by both the sterol regulatory element binding protein (SREBP) SrbA, and the CCAAT binding complex (CBC). We show that the CBC acts complementary to SrbA as a negative regulator of ergosterol biosynthesis and show that lack of CBC activity results in increased sterol levels via transcriptional derepression of multiple ergosterol biosynthetic genes including those coding for HMG-CoA-synthase, HMG-CoA-reductase and sterol C14-demethylase. In agreement with these findings, inactivation of the CBC increased tolerance to different classes of drugs targeting ergosterol biosynthesis including the azoles, allylamines (terbinafine) and statins (simvastatin). We reveal that a clinically relevant mutation in HapE (P88L) significantly impairs the binding affinity of the CBC to its target site. We identify that the mechanism underpinning TR34 driven overexpression of cyp51A results from duplication of SrbA but not CBC binding sites and show that deletion of the 34 mer results in lack of cyp51A expression and increased azole susceptibility similar to a cyp51A null mutant. Finally we show that strains lacking a functional CBC are severely attenuated for pathogenicity in a pulmonary and systemic model of aspergillosis.

Aspergillus fumigatus is the most important airborne mould pathogen and allergen worldwide. Estimates suggest that >3 million people have invasive or chronic infections that lead to >600,000 deaths every year. Very few drugs are available to treat the various forms of aspergillosis and we rely predominantly on the azole class of agents which inhibit sterol biosynthesis. Resistance to the azoles is growing alarmingly, primarily driven by strains with two principal genetic signatures (TR₃₄/L98H and TR₄₆/Y121F/T289A). In this study we identify that the transcriptional mechanism governing resistance in this group of isolates is linked to the opposing actions of 2 transcriptional regulators, SrbA and the CBC, and uncover a role for the CBC in sterol regulation and virulence in A. fumigatus. We propose targeting SrbA would provide an effective avenue for therapeutic intervention for resistant strains.

Characterization of Fosfomycin Resistance Gene, fosB, in Methicillin-Resistant Staphylococcus aureus Isolates

To investigate the prevalence, location and genetic environments of fosfomycin-resistance (fos) genes in methicillin-resistant Staphylococcus aureus (MRSA) clinical strains, 67 fosfomycin-resistant MRSA strains were isolated from the blood and cerebrospinal fluid samples at a teaching hospital in Shanghai. The presence of fos genes in these clinical strains was detected by PCR and sequencing. The locations of fos genes were determined by Southern blotting and genetic environments were analyzed by primer walking sequencing. Multiple locus sequence typing (MLST) was used to characterize genetic diversity. Conjugation was performed to evaluate the transferability of fos genes. Among 67 fosfomycin-resistant MRSA strains, nine high level fosfomycin resistant strains (≥128 μg/ml) were fosB-positive. Three new subtypes of fosB, designated as fosB4, fosB5, and fosB6, were identified. fosB1, fosB4 or fosB6 genes were located on small plasmids (ca. 2.5 kb) and flanked by an analogous replication gene (rep). Differently, the fosB5 gene was surrounded by a shorter rep gene and two copies of a transposon gene (tnp) that shared high identity with the IS257-like transposon. Four MLST types were found among the nine fosB-positive strains. Transconjugants with the fosB genes were resistant to fosfomycin with MIC 64 or 128 μg/ml. In conclusion, different subtypes and genetic environment of fosB genes indicate that gene heterogeneity for fosfomycin resistance in MRSA isolates.

Prevalence of Fosfomycin Resistance and Mutations in murA, glpT, and uhpT in Methicillin-Resistant Staphylococcus aureus Strains Isolated from Blood and Cerebrospinal Fluid Samples

In China, fosfomycin alone or in combination with other antibiotics is commonly used in the treatment of infections caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA). Although fosfomycin-resistant S. aureus strains have continued to emerge and increase, the research on them is rare. In order to determine the prevalence and mechanisms of fosfomycin resistance in MRSA clinical isolates, a total of 96 non-duplicate MRSA isolates were collected from blood and cerebrospinal fluid samples at Huashan Hospital in Shanghai, China between 2004 and 2014. Antimicrobial susceptibility testing was performed by agar dilution. Meanwhile, the fosfomycin-resistance-related genes, fosB, murA, glpT, and uhpT, were amplified by PCR and subjected to sequencing analysis. Multilocus sequence typing (MLST) was conducted to assess strain types. The minimum inhibitory concentration (MIC) of fosfomycin for the 96 MRSA strains ranged from 1.0 to >1,024 mg/L, and approximately 70% (67/96) of the isolates were resistant to fosfomycin (MIC ≥ 64.0 mg/L). Nine isolates with MICs ≥ 128 mg/L carried fosB gene. Twenty-five distinct mutations were detected in the murA (7), glpT (10), and uhpT (8) genes. While five of the murA mutations and five of the glpT mutations were observed only in fosfomycin-sensitive isolates and one of the murA mutation was found both in fosfomycin-resistant and fosfomycin-sensitive isolates, the remaining 14 mutations (1 murA, 5 glpT, and all uhpT mutations) were present only in fosfomycin-resistant isolates. MLST analysis demonstrated that the majority (46/67) of the glpT and/or uhpT mutants belong to ST5, the predominant sequence type among the fosfomycin-resistant MRSA isolates. In conclusion, there is a high rate of fosfomycin resistance in MRSA strains. The mutations in the murA, glpT, and uhpT genes are common in fosfomycin-resistant MRSA strains, and may play a greater role in the development of fosfomycin resistance than the presence of the fosB gene in these organisms.

Azole Resistance in Aspergillus fumigatus Clinical Isolates from an Italian Culture Collection

The aims of the study were to investigate the prevalence of azole resistance among Aspergillus fumigatus clinical isolates. A total of 533 clinical isolates that had been collected between 1995 and 2006, from 441 patients, were screened. No resistance was detected in isolates collected between 1995 and 1997. Starting in 1998, the resistance rate was 6.9%; a total of 24 patients (6.25%) harbored a resistant isolate. The TR34/L98H substitution was found in 21 of 30 tested isolates.

Diagnostic of Fungal Infections Related to Biofilms

Fungal biofilm-related infections, most notably those caused by the Candida and Aspergillus genera, need to be diagnosed accurately and rapidly to avoid often unfavorable outcomes. Despite diagnosis of these infections is still based on the traditional histopathology and culture, the use of newer, rapid methods has enormously enhanced the diagnostic capability of a modern clinical mycology laboratory. Thus, while accurate species-level identification of fungal isolates can be achieved with turnaround times considerably shortened, nucleic acid-based or antigen-based detection methods can be considered useful adjuncts for the diagnosis of invasive forms of candidiasis and aspergillosis. Furthermore, simple, reproducible, and fast methods have been developed to quantify biofilm production by fungal isolates in vitro. In this end, isolates can be categorized as low, moderate, or high biofilm-forming, and this categorization may reflect their differential response to the conventional antifungal therapy. By means of drug susceptibility testing performed on fungal biofilm-growing isolates, it is now possible to evaluate not only the activity of conventional antifungal agents, but also of novel anti-biofilm agents. Despite this, future diagnostic methods need to target specific biofilm components/molecules, in order to provide a direct proof of the presence of this growth phenotype on the site of infection. In the meantime, our knowledge of the processes underlying the adaptive drug resistance within the biofilm has put into evidence biofilm-specific molecules that could be potentially helpful as therapeutic targets. Surely, the successful management of clinically relevant fungal biofilms will rely upon the advancement and/or refinement of these approaches.

Amphotericin B Resistance in Aspergillus terreus Is Overpowered by Coapplication of Pro-oxidants

AIMS

Invasive fungal infections have significantly increased over the past decades in immunocompromised individuals and high-risk patients. Amphotericin B (AmB) exerts a powerful and broad activity against a vast array of fungi and has a remarkably low rate of microbial resistance. However, most isolates of Aspergillus terreus developed an intrinsic resistance against AmB, and during this study, we characterized the mode of action of this polyene antifungal drug in more detail in resistant (ATR) and rare susceptible (ATS) clinical isolates of A. terreus.

RESULTS

We illustrate that AmB treatment changes cellular redox status and promotes the generation of high levels of reactive oxygen species (ROS) in ATS. In contrast, ATR isolates were able to cope better with AmB-induced oxidative stress.

INNOVATION

Most importantly, we demonstrate in this study that coapplication of anti- and pro-oxidants significantly affects AmB efficacy in an antithetic manner--antioxidants and ROS-scavenging agents increase AmB tolerance in susceptible strains, while pro-oxidants render formerly resistant isolates considerably susceptible to the antifungal drug also in vivo in a Galleria animal model.

CONCLUSION

Thereby, our study provides novel therapeutic options to treat formerly resistant fungal strains by a combination of AmB and pro-oxidant compounds.

In Vitro Activity of Isavuconazole and Comparators against Clinical Isolates of the Mucorales Order

The in vitro activity of isavuconazole against Mucorales isolates measured by EUCAST E.Def 9.2 and CLSI M38-A2 methodologies was investigated in comparison with those of amphotericin B, posaconazole, and voriconazole. Seventy-two isolates were included: 12 of Lichtheimia corymbifera, 5 of Lichtheimia ramosa, 5 of group I and 9 of group II of Mucor circinelloides, 9 of Rhizomucor pusillus, 26 of Rhizopus microsporus, and 6 of Rhizopus oryzae. Species identification was confirmed by internal transcribed spacer (ITS) sequencing. EUCAST MICs were read on day 1 (EUCAST-d1) and day 2 (EUCAST-d2), and CLSI MICs were read on day 2 (CLSI-d2). Isavuconazole MIC50s (range) (mg/liter) by EUCAST-d1, CLSI-d2, and EUCAST-d2 were 1 (0.125 to 16), 1 (0.125 to 2), and 4 (0.5 to >16), respectively, across all isolates. The similar values for comparator drugs were as follows: posaconazole, 0.25 (≤ 0.03 to >16), 0.25 (0.06 to >16), and 1 (0.06 to >16); amphotericin, 0.06 (≤ 0.03 to 0.5), 0.06 (≤ 0.03 to 0.25), and 0.125 (≤ 0.03 to 1); voriconazole, 16 (2 to >16), 8 (1 to >16), and >16 (8 to >16), respectively. Isavuconazole activity varied by species: Lichtheimia corymbifera, 1 (0.5 to 2), 1 (1 to 2), and 2 (1 to 4); Lichtheimia ramosa, 0.25 (0.125 to 0.5), 1 (0.5 to 2), and 2 (0.5 to 4); Rhizomucor pusillus, 0.5 (0.5 to 1), 1 (0.125 to 1), and 2 (1 to 2); Rhizopus microsporus, 1 (0.5 to 4), 0.5 (0.125 to 1), and 4 (1 to 8); and Rhizopus oryzae, 1 (0.5 to 4), 1 (0.125 to 2), and 4 (0.5 to 8), respectively, were more susceptible than Mucor circinelloides: group I, 8 (4 to 8), 4 (2 to 4), and 16 (2 to 16), respectively, and group II, 8 (1 to 16), 8 (1 to 8), and 16 (4 to >16), respectively. This was also observed for posaconazole. The essential agreement was best between EUCAST-d1 and CLSI-d2 (75% to 83%). Isavuconazole displayed in vitro activity against Mucorales isolates with the exception of Mucor circinelloides. The MICs were in general 1 to 3 steps higher than those for posaconazole. However, in the clinical setting this may be compensated for by the higher exposure at standard dosing.

A Nano-MgO and Ionic Liquid-Catalyzed 'Green' Synthesis Protocol for the Development of Adamantyl-Imidazolo-Thiadiazoles as Anti-Tuberculosis Agents Targeting Sterol 14α-Demethylase (CYP51)

In this work, we describe the 'green' synthesis of novel 6-(adamantan-1-yl)-2-substituted-imidazo[2,1-b][1,3,4]thiadiazoles (AITs) by ring formation reactions using 1-(adamantan-1-yl)-2-bromoethanone and 5-alkyl/aryl-2-amino1,3,4-thiadiazoles on a nano material base in ionic liquid media. Given the established activity of imidazothiadiazoles against M. tuberculosis, we next examined the anti-TB activity of AITs against the H37Rv strain using Alamar blue assay. Among the tested compounds 6-(adamantan-1-yl)-2-(4-methoxyphenyl)imidazo[2,1-b][1,3,4]thiadiazole (3f) showed potent inhibitory activity towards M. tuberculosis with an MIC value of 8.5 μM. The inhibitory effect of this molecule against M. tuberculosis was comparable to the standard drugs such as Pyrazinamide, Streptomycin, and Ciprofloxacin drugs. Mechanistically, an in silico analysis predicted sterol 14α-demethylase (CYP51) as the likely target and experimental activity of 3f in this system corroborated the in silico target prediction. In summary, we herein report the synthesis and biological evaluation of novel AITs against M. tuberculosis that likely target CYP51 to induce their antimycobacterial activity.

Galleria mellonella as a host model to study Aspergillus terreus virulence and amphotericin B resistance

The aim of this study was to investigate if the alternative in vivo model Galleria mellonella can be used (i) to determine differences in pathogenicity of amphotericin B (AMB) resistant and susceptible A. terreus isolates, (ii) to evaluate AMB efficacy in vivo (iii) and to correlate outcome to in vitro susceptibility data. Larvae were infected with 2 A. terreus AMB resistant (ATR) and 3 AMB susceptible (ATS) isolates and survival rates were correlated to physiological attributes and killing ability of larval haemocytes. Additionally, infected larvae were treated with different concentrations of L-AMB. Haemocyte density were ascertained to evaluate the influence of L-AMB on the larval immune cells. Larvae were sensitive to A. terreus infection in an inoculum-size and temperature dependent manner. In vitro susceptibility to L-AMB correlated with in vivo outcome of antifungal treatment, defining an AMB susceptible strain cluster of A. terreus. Susceptibility to L-AMB increased virulence potential in the larval model, but this increase was also in accordance with faster growth and less damage caused by larval haemocytes. L-AMB treatment primed the larval immune response by increasing haemocyte density. G. mellonella provides a convenient model for the in vivo screening of A. terreus virulence and treatment options, contributing to the generation of a hypothesis that can be further tested in refined experiments in mammalian models.

Isavuconazole: a new extended spectrum triazole for invasive mold diseases

ABSTRACT 

Isavuconazole is the first broad spectrum prodrug triazole with efficacy against invasive fungal diseases including aspergillosis and mucormycosis. Characteristics include linear dose-proportional pharmacokinetics, intravenous and oral formulations allowing therapeutic streamlining, once daily dosing, absence of nephrotoxic solubilizing agents and excellent oral bioavailability independent of prandial status and gastric acidity. An open label noncomparator study demonstrated encouraging results for isavuconazole as primary or salvage therapy for a range of fungi including mucormycosis. Isavuconazole had fewer premature drug discontinuations and adverse events in the eye, hepatobiliary and psychiatry systems than the comparator agent, voriconazole in a randomized double-blind clinical trial. Cross-resistance of isavuconazole best correlates with voriconazole. In vitro resistance is not invariably predictive of clinical failure. Isavuconazole signals progress in pharmacokinetics, bioavailability and toxicity/tolerability supported by clinical efficacy from Phase III trials.

Azole-resistant aspergillosis

Azole-resistance in Aspergillus fumigatus is emerging and is becoming an increasing problem in the management of aspergillosis. Two types of development of resistance have been described; resistance acquired during azole treatment in an individual patient and through environmental exposure to fungicides. The main molecular mechanism of azole resistance in A. fumigatus is explained by mutations in the cyp51A-gene. The environmental route of resistance development is particularly worrying and may affect all patients whether azole exposed or naïve, and whether suffering from acute or chronic aspergillosis. No management guidelines to assist clinicians confronted with azole-resistant aspergillosis are available and pre-clinical and clinical evidence supporting treatment choices is scarce.

First detection of Aspergillus fumigatus azole-resistant strain due to Cyp51A TR46/Y121F/T289A in an azole-naive patient in Spain

We report the first isolation of a voriconazole-resistant Aspergillus fumigatus strain harbouring the azole resistance mechanism TR46/Y121F/T289A, recovered from an azole-naive patient in Spain with chronic obstructive pulmonary disease. This new finding in Spain suggests the spread of this resistance mechanism and reinforces the need for antifungal susceptibility surveillance.

Blocking Hsp70 enhances the efficiency of amphotericin B treatment against resistant Aspergillus terreus strains

The polyene antifungal amphotericin B (AmB) is widely used to treat life-threatening fungal infections. Even though AmB resistance is exceptionally rare in fungi, most Aspergillus terreus isolates exhibit an intrinsic resistance against the drug in vivo and in vitro. Heat shock proteins perform a fundamental protective role against a multitude of stress responses, thereby maintaining protein homeostasis in the organism. In this study, we elucidated the role of heat shock protein 70 (Hsp70) family members and compared resistant and susceptible A. terreus clinical isolates. The upregulation of cytoplasmic Hsp70 members at the transcriptional as well as translational levels was significantly higher with AmB treatment than without AmB treatment, particularly in resistant A. terreus isolates, thereby indicating a role of Hsp70 proteins in the AmB response. We found that Hsp70 inhibitors considerably increased the susceptibility of resistant A. terreus isolates to AmB but exerted little impact on susceptible isolates. Also, in in vivo experiments, using the Galleria mellonella infection model, cotreatment of resistant A. terreus strains with AmB and the Hsp70 inhibitor pifithrin-μ resulted in significantly improved survival compared with that achieved with AmB alone. Our results point to an important mechanism of regulation of AmB resistance by Hsp70 family members in A. terreus and suggest novel drug targets for the treatment of infections caused by resistant fungal isolates.

The molecular mechanism of azole resistance in Aspergillus fumigatus: from bedside to bench and back

The growing use of immunosuppressive therapies has resulted in a dramatic increased incidence of invasive fungal infections (IFIs) caused by Aspergillus fumigatus, a common pathogen, and is also associated with a high mortality rate. Azoles are the primary guideline-recommended therapy agents for first-line treatment and prevention of IFIs. However, increased azole usage in medicinal and agricultural settings has caused azole-resistant isolates to repeatedly emerge in the environment, resulting in a significant threat to human health. In this review, we present and summarize current research on the resistance mechanisms of azoles in A. fumigatus as well as efficient susceptibility testing methods. Moreover, we analyze and discuss the putative clinical (bedside) indication of these findings from bench work.

An international cross-sectional survey of antimicrobial stewardship programmes in hospitals

OBJECTIVES

To report the extent and components of global efforts in antimicrobial stewardship (AMS) in hospitals.

METHODS

An Internet-based survey comprising 43 questions was disseminated worldwide in 2012.

RESULTS

Responses were received from 660 hospitals in 67 countries: Africa, 44; Asia, 50; Europe, 361; North America, 72; Oceania, 30; and South and Central America, 103. National AMS standards existed in 52% of countries, 4% were planning them and 58% had an AMS programme. The main barriers to implementing AMS programmes were perceived to be a lack of funding or personnel, a lack of information technology and prescriber opposition. In hospitals with an existing AMS programme, AMS rounds existed in 64%; 81% restricted antimicrobials (carbapenems, 74.3%; quinolones, 64%; and cephalosporins, 58%); and 85% reported antimicrobial usage, with 55% linking data to resistance rates and 49% linking data to infection rates. Only 20% had electronic prescribing for all patients. A total of 89% of programmes educated their medical, nursing and pharmacy staff on AMS. Of the hospitals, 38% had formally reviewed their AMS programme: reductions were reported by 96% of hospitals for inappropriate prescribing, 86% for broad-spectrum antibiotic use, 80% for expenditure, 71% for healthcare-acquired infections, 65% for length of stay or mortality and 58% for bacterial resistance.

CONCLUSIONS

The worldwide development and implementation of AMS programmes varies considerably. Our results should inform and encourage the further evaluation of this with a view to promoting a worldwide stewardship framework. The prospective measurement of well-defined outcomes of the impact of these programmes remains a significant challenge.

EUCAST testing of Isavuconazole susceptibility in Aspergillus: comparison of results for Inoculum standardization using Conidium counting versus optical density

The EUCAST E.DEF9.1 standard recommends standardization of the inoculum concentration by conidium counting using a hemocytometer rather than a spectrophotometer. In this study, we investigated whether the choice of these methods influenced isavuconazole MICs. A blinded collection of 30 molecularly characterized azole-resistant isolates and 10 wild-type Aspergillus fumigatus isolates was shared with four different laboratories. Additionally, each laboratory selected approximately 100 A. fumigatus isolates and 50 isolates each of A. flavus, A. nidulans, A. niger, and A. terreus (1,237 isolates in total). Three laboratories (laboratories 1 to 3) used conidium counting. One laboratory standardized the inoculum using a spectrophotometer (that is, by use of the optical density [OD]) and is referred to as the OD laboratory. Correlation coefficients, intraclass correlation coefficients, and essential agreement were calculated, and 2-log-unit differences were assessed (paired t test). The MIC range for the blinded collection was 0.25 to 16 mg/liter, and a 1-dilution-step difference between the MIC50 and MIC90 across the four laboratories was detected and a 2-dilution-step difference between the modal MICs was detected. Compared to the results for laboratories 1 and 2, a significant correlation was found for the OD laboratory MIC data (correlation coefficients, 0.85 and 0.93, respectively; intraclass correlation coefficients, 0.88 and 0.96, respectively). The number of mutant isolates whose MICs overlapped those of the wild-type isolates was the lowest for the OD laboratory (14/30 [46.7%] mutant isolates), whereas the numbers were 18/30 (60%) isolates for laboratory 1, 17/30 (56.7%) isolates for laboratory 2, and 21/30 (70%) isolates for laboratory 3. For the A. flavus, A. fumigatus, A. nidulans, A. niger, and A. terreus isolates, comparative analysis again defined the MIC distributions from the OD laboratory to be in excellent agreement with those from laboratories 1 and 2 across all five Aspergillus spp. The findings suggest that EUCAST testing using OD determination is an appropriate alternative for standardization of Aspergillus inoculum concentrations.

The role of azoles in the management of azole-resistant aspergillosis: from the bench to the bedside

Azole resistance is an emerging problem in Aspergillus fumigatus and is associated with a high probability of treatment failure. An azole resistance mechanism typically decreases the activity of multiple azole compounds, depending on the mutation. As alternative treatment options are limited and in some isolates the minimum inhibitory concentration (MIC) increases by only a few two-fold dilutions steps, we investigated if voriconazole and posaconazole have a role in treating azole-resistant Aspergillus disease. The relation between resistance genotype and phenotype, pharmacokinetic and pharmacodynamic properties, and (pre)clinical treatment efficacy were reviewed. The results were used to estimate the exposure needed to achieve the pharmacodynamic target for each MIC. For posaconazole adequate exposure can be achieved only for wild type isolates as dose escalation does not allow PD target attainment. However, the new intravenous formulation might result in sufficient exposure to treat isolates with a MIC of 0.5 mg/L. For voriconazole our analysis indicated that the exposure needed to treat infection due to isolates with a MIC of 2 mg/L is feasible and maybe isolates with a MIC of 4 mg/L. However, extreme caution and strict monitoring of drug levels would be required, as the probability of toxicity will also increase.

Current status of antifungal resistance and its impact on clinical practice

Mortality linked to invasive fungal diseases remains very high despite the availability of novel antifungals and new therapeutic strategies. Candida albicans and Aspergillus fumigatus account for most invasive mycosis produced by yeast or moulds, respectively. Other Candida non-albicans are increasingly being reported and newly emerging, as well as cryptic, filamentous fungi often cause disseminated infections in immunocompromised hosts. Management of invasive fungal infections is becoming a challenge as emerging fungal pathogens generally show poor response to many antifungals. The ability of reference antifungal susceptibility testing methods to detect emerging resistance patterns, together with the molecular characterization of antifungal resistance mechanisms, are providing useful information to optimize the effectiveness of antifungal therapy. The current status of antifungal resistance epidemiology with special emphasis on the molecular resistant mechanisms that have been described in the main pathogenic fungal species are reviewed.

Azole-resistant Aspergillus fumigatus in the environment of northern Italy, May 2011 to June 2012

In recent years acquired azole resistance in Aspergillus fumigatus has been increasingly reported and a dominant mechanism of resistance (TR34/L98H) was found in clinical and environmental isolates. The aim of the present study was to investigate the prevalence of azole resistance in environmental A. fumigatus isolates collected in northern Italy. A. fumigatus grew from 29 of 47 soil samples analysed. Azole-resistant isolates were detected in 13% (6/47) of the soil samples and in 21% (6/29) of the soil samples containing A. fumigatus. High minimal inhibitory concentrations (MIC) of itraconazole (≥16 mg/L) and posaconazole (≥0.5 mg/L) were displayed by nine isolates from six different soil samples, namely apple orchard (1 sample), rose pot compost (2 samples), and cucurbit yields (3 samples). Seven isolates had a MIC=2 mg/L of voriconazole. Seven of nine itraconazole and posaconazole resistant isolates harboured the same TR34/L98H mutation of cyp51A. These findings, together with the occurrence of resistant clinical isolates, suggest that azole resistance should be considered in primary patient care.

Susceptibility breakpoints for amphotericin B and Aspergillus species in an in vitro pharmacokinetic-pharmacodynamic model simulating free-drug concentrations in human serum

Although conventional amphotericin B was for many years the drug of choice and remains an important agent against invasive aspergillosis, reliable susceptibility breakpoints are lacking. Three clinical Aspergillus isolates (Aspergillus fumigatus, Aspergillus flavus, and Aspergillus terreus) were tested in an in vitro pharmacokinetic-pharmacodynamic model simulating the biphasic 24-h time-concentration profile of free amphotericin B concentrations in human serum with free peak concentrations (fCmax) of 0.1, 0.3, 0.6, 1.2, and 2.4 mg/liter administered once daily. Drug concentrations were measured with a bioassay, and fungal growth was monitored for 72 h with galactomannan production. The fCmax/MIC corresponding to half-maximal activity (P50) was determined for each species, and the percentage of target attainment was calculated for different MICs for the standard (1 mg/kg of body weight) and a lower (0.6-mg/kg) dose of amphotericin B with Monte Carlo simulation analysis. The fCmax/MICs (95% confidence intervals) corresponding to P50 were 0.145 (0.133 to 0.158), 0.371 (0.283 to 0.486), and 0.41 (0.292 to 0.522) for A. fumigatus, A. flavus, and A. terreus, respectively. The median percentages of P50 attainment were ≥88%, 47%, and 0% for A. fumigatus isolates with MICs of ≤0.5, 1, and ≥2 mg/liter, respectively, and ≥81%, 24%, and 0% and ≥75%, 15%, and 0% for A. flavus and A. terreus isolates with MICs of ≤0.25, 0.5, and ≥1 mg/liter, respectively. The lower dose of 0.6 mg/kg would retain efficacy for A. fumigatus, A. flavus, and A. terreus isolates with MICs of ≤0.25, ≤0.125, and ≤0.125 mg/liter, respectively. The susceptibility, intermediate susceptibility, and resistance breakpoints of ≤0.5, 1, and ≥2 mg/liter for A. fumigatus and ≤0.25, 0.5, and ≥1 mg/liter for A. flavus and A. terreus were determined for conventional amphotericin B with a pharmacokinetic-pharmacodynamic model simulating free-drug serum concentrations.

Susceptibility testing in Aspergillus species complex

Methods for susceptibility testing of Aspergillus are developed and validated by the European Committee on Antibiotic Susceptibility Testing Subcommittee on Antifungal Susceptibility Testing. Breakpoints for phenotypic antimicrobial susceptibility testing have been determined by breakpoint committees and as part of regulatory processes for the approval of new drugs. Dosages, pharmacokinetics, resistance mechanisms, MIC distributions, pharmacodynamics and epidemiological cut-off values are used in the breakpoint-setting process. Clinical breakpoints are for everyday use in the clinical laboratory to advise on patient therapy. Resistance in Aspergillus fumigatus has been increasingly reported since standards became available.

Update on antifungal resistance in Aspergillus and Candida

Antifungal resistance in Candida and Aspergillus may be either intrinsic or acquired and may be encountered in the antifungal drug exposed but also the antifungal drug-naïve patient. Prior antifungal treatment confers a selection pressure and notoriously raises the awareness of possible resistance in patients failing therapy, thus calling for susceptibility testing. On the contrary, antifungal resistance in the drug-naïve patient is less expected and therefore more challenging. This is particularly true when it concerns pathogens with acquired resistance which cannot be predicted from the species identification itself. This scenario is particularly relevant for A. fumigatus infections due to the increasing prevalence of azole-resistant isolates in the environment. For Candida, infections resistance is most common in the context of increasing prevalence of species with intrinsic resistance. Candida glabrata which has intrinsically reduced susceptibility to fluconazole is increasingly common particularly among the adult and elderly population on the Northern Hemisphere where it may be responsible for as many as 30% of the blood stream infections in population-based surveillance programmes. Candida parapsilosis is prevalent in the paediatric setting, at centres with increasing echinocandin use and at the southern or pacific parts of the world. In the following, the prevalence and drivers of intrinsic and acquired resistance in Aspergillus and Candida will be reviewed.

Breakpoints for antifungal agents: an update from EUCAST focussing on echinocandins against Candida spp. and triazoles against Aspergillus spp

Candida and Aspergillus infections have emerged as significant pathogens in recent decades. During this same time, broad spectrum triazole and echinocandin antifungal agents have been developed and increasingly used. One consequence of widespread use is leading to the emergence of mutants with acquired resistance mutations. Therefore, accurate susceptibility testing and appropriate clinical breakpoints for the interpretation of susceptibility results have become increasingly important. Here we review the underlying methodology by which breakpoints have been selected by EUCAST (European Committee on Antimicrobial Susceptibility Testing). Five parameters are evaluated: dosing regimens used; EUCAST MIC distributions from multiple laboratories, species and compound specific epidemiological cut off values (upper MIC limits of wild type isolates or ECOFFs), pharmacokinetic/pharmacodynamic relationships and targets associated with outcome and finally clinical data by species and MIC when available. The general principles are reviewed followed by a detailed review of the individual aspects for Candida species and the three echinocandins and for Aspergillus and the three mould-active azoles. This review provides an update of the subcommittee on antifungal susceptibility testing (AFST) of the EUCAST methodology and summarises the current EUCAST breakpoints for Candida and Aspergillus. Recommendations about applicability of antifungal susceptibility testing in the routine setting are also included.

Therapeutic drug monitoring (TDM) of antifungal agents: guidelines from the British Society for Medical Mycology

The burden of human disease related to medically important fungal pathogens is substantial. An improved understanding of antifungal pharmacology and antifungal pharmacokinetics-pharmacodynamics has resulted in therapeutic drug monitoring (TDM) becoming a valuable adjunct to the routine administration of some antifungal agents. TDM may increase the probability of a successful outcome, prevent drug-related toxicity and potentially prevent the emergence of antifungal drug resistance. Much of the evidence that supports TDM is circumstantial. This document reviews the available literature and provides a series of recommendations for TDM of antifungal agents.

Determination of isavuconazole susceptibility of Aspergillus and Candida species by the EUCAST method

Isavuconazole is a novel expanded-spectrum triazole, which has recently been approved by the FDA as an orphan drug to treat invasive aspergillosis and is currently being studied in phase III clinical trials for invasive candidiasis. The susceptibility of relatively few clinical isolates has been reported. In this study, the isavuconazole susceptibilities of 1,237 Aspergillus and 2,010 Candida geographically diverse clinical isolates were determined by EUCAST methodology at four European mycology laboratories, producing the largest multicenter data set thus far for this compound. In addition, a blinded collection of 30 cyp51A mutant Aspergillus fumigatus clinical isolates and 10 wild-type isolates was tested. From these two data sets, the following preliminary epidemiological cutoff (ECOFF) values were suggested: 2 mg/liter for Aspergillus fumigatus, Aspergillus terreus, and Aspergillus flavus; 4 mg/liter for Aspergillus niger; 0.25 mg/liter for Aspergillus nidulans; and 0.03 mg/liter for Candida albicans, Candida parapsilosis, and Candida tropicalis. Unfortunately, ECOFFs could not be determined for Candida glabrata or Candida krusei due to an unexplained interlaboratory MIC variation. For the blinded collection of A. fumigatus isolates, all MICs were ≤2 mg/liter for wild-type isolates. Differential isavuconazole MICs were observed for triazole-resistant A. fumigatus isolates with different cyp51A alterations: TR34/L98H mutants had elevated isavuconazole MICs, whereas isolates with G54 and M220 alterations had MICs in the wild-type range, suggesting that the efficacy of isavuconazole may not be affected by these alterations. This study will be an aid in interpreting isavuconazole MICs for clinical care and an important step in the future process of setting official clinical breakpoints.

Population-based survey of filamentous fungi and antifungal resistance in Spain (FILPOP Study)

A population-based survey was conducted to investigate the epidemiology of and antifungal resistance in Spanish clinical strains of filamentous fungi isolated from deep tissue samples, blood cultures, and respiratory samples. The study was conducted in two different periods (October 2010 and May 2011) to analyze seasonal variations. A total of 325 strains were isolated in 29 different hospitals. The average prevalence was 0.016/1,000 inhabitants [corrected]. Strains were identified by sequencing of DNA targets and susceptibility testing by the European Committee for Antimicrobial Susceptibility Testing reference procedure. The most frequently isolated genus was Aspergillus, accounting for 86.3% of the isolates, followed by Scedosporium at 4.7%; the order Mucorales at 2.5%; Penicillium at 2.2%, and Fusarium at 1.2%. The most frequent species was Aspergillus fumigatus (48.5%), followed by A. flavus (8.4%), A. terreus (8.1%), A. tubingensis (6.8%), and A. niger (6.5%). Cryptic/sibling Aspergillus species accounted for 12% of the cases. Resistance to amphotericin B was found in 10.8% of the isolates tested, while extended-spectrum triazole resistance ranged from 10 to 12.7%, depending on the azole tested. Antifungal resistance was more common among emerging species such as those of Scedosporium and Mucorales and also among cryptic species of Aspergillus, with 40% of these isolates showing resistance to all of the antifungal compounds tested. Cryptic Aspergillus species seem to be underestimated, and their correct classification could be clinically relevant. The performance of antifungal susceptibility testing of the strains implicated in deep infections and multicentric studies is recommended to evaluate the incidence of these cryptic species in other geographic areas.

Itraconazole: an update on pharmacology and clinical use for treatment of invasive and allergic fungal infections

INTRODUCTION

Fungal infections are a major source of global morbidity and mortality. Itraconazole is a triazole antifungal agent that is widely used for the prevention and treatment of fungal infection. While newer antifungal agents are now available, itraconazole is an orally bioavailable agent with broad-spectrum antifungal activity. Itraconazole remains a useful drug for the management of allergic and invasive mycoses worldwide.

AREAS COVERED

This article provides a summary of the pharmacokinetics, pharmacodynamics and clinical uses of itraconazole. Additionally, the authors summarise the safety and recently described toxicodynamics and discuss the value of therapeutic drug monitoring (TDM) with itraconazole. The following search criteria were constructed in order to identify relevant literature using PubMed and Ovid-MEDLINE: itraconazole, triazole, pharmacokinetics, pharmacodynamics, toxicodynamics and TDM. Relevant abstracts and articles identified from reviewing secondary citations were additionally retrieved and included if relevant.

EXPERT OPINION

Itraconazole remains an important agent in the prevention and treatment of fungal infection. Itraconazole has a broad-spectrum of activity and is available in both an intravenous and oral form making long-term use in chronic mycoses practical. Itraconazole is widely used for the treatment of endemic fungal infections. Pharmacokinetic variability and clinically important drug interactions make TDM of itraconazole an important consideration.

Comparison of Rosco Neo-Sensitabs with Oxoid paper disks in EUCAST disk diffusion antimicrobial susceptibility testing on Mueller-Hinton agar

This study compared Neo-Sensitabs with Oxoid paper disks using the European Committee on Antimicrobial Susceptibility Testing (EUCAST) disk diffusion antimicrobial susceptibility test on Mueller-Hinton agar. The EUCAST-recommended quality control strains (Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212) (Part I) and clinical isolates (Part II) were investigated. In Part I of the study, 27 combinations of antimicrobial agents were tested on four quality control strains repeatedly up to 60 times and zone diameters of tablets and disks were compared. In Part II of the study, 351 clinical isolates were included to cover a broad range of species, as well as resistance mechanisms. In Part I, four major deviations (>1 mm outside quality control ranges) were observed with Neo-Sensitabs. In one case with P. aeruginosa ATCC 27853 (meropenem), there was a corresponding major deviation (2 mm) with the Oxoid disk. The three remaining major deviations with Neo-Sensitabs were observed with meropenem (2 mm) in E. coli ATCC 25922 and with ciprofloxacin (2 mm) and gentamicin (3 mm) in P. aeruginosa ATCC 27853. For Oxoid disks, there were only minor deviations (=1 mm outside quality control ranges) in these three cases. In Part II, there were six discrepancies, susceptible versus resistant, in 3,533 comparisons between the two methods with the clinical isolates. The Rosco Neo-Sensitabs appear to be a possible alternative to Oxoid paper disks for EUCAST disk diffusion antimicrobial susceptibility testing on Mueller-Hinton agar.

Pharmacodynamics of itraconazole against Aspergillus fumigatus in an in vitro model of the human alveolus: perspectives on the treatment of triazole-resistant infection and utility of airway administration

Itraconazole is used for the prevention and treatment of infections caused by Aspergillus fumigatus. An understanding of the pharmacodynamics of itraconazole against wild-type and triazole-resistant strains provides a basis for innovative therapeutic strategies for treatment of infections. An in vitro model of the human alveolus was used to define the pharmacodynamics of itraconazole. Galactomannan was used as a biomarker. The effect of systemic and airway administration of itraconazole was assessed, as was a combination of itraconazole administered to the airway and systemically administered 5FC. Systemically administered itraconazole against the wild type induced a concentration-dependent decline in galactomannan in the alveolar and endothelial compartments. No exposure-response relationships were apparent for the L98H, M220T, or G138C mutant. The administration of itraconazole to the airway resulted in comparable exposure-response relationships to those observed with systemic therapy. This was achieved without detectable concentrations of drug within the endothelial compartment. The airway administration of itraconazole resulted in a definite but submaximal effect in the endothelial compartment against the L98H mutant. The administration of 5FC resulted in a concentration-dependent decline in galactomannan in both the alveolar and endothelial compartments. The combination of airway administration of itraconazole and systemically administered 5FC was additive. Systemic administration of itraconazole is ineffective against Cyp51 mutants. The airway administration of itraconazole is effective for the treatment of wild-type strains and appears to have some activity against the L98H mutants. Combination with other agents, such as 5FC, may enable the attainment of near-maximal antifungal activity.

Microevolution of a zoonotic Helicobacter population colonizing the stomach of a human host before and after failed treatment

To investigate the microevolution of Helicobacter bizzozeronii in the human stomach, comparative genomics of antrum-derived populations, obtained 3 months before (T(0)) and 6 months after (T(1)) an unsuccessful eradication treatment, was performed. For each time point, the DNA of bacterial mass, representing the population diversity in three biopsies, was mixed in equal amounts and sequenced using Illumina technology. Polymorphic sites (PSs) were detected by mapping the reads against an isogenic reference genome, derived from a corpus isolate obtained at T(0). The total numbers of PSs detected in the H. bizzozeronii population at T(0) and T(1) were 128 and 223, affecting 81 and 134 coding sequences, respectively. At T(0) in 91.4% of the PSs the mutation appeared at a frequency of 50% or less. On the contrary, in the majority of the PSs observed in T(1) (71.3%) the mutation had a frequency >75%. Although only a minority of mutations were fixed in the antrum-derived population at T(0), a certain level of allelic variability, compared with the corpus-derived reference genome, was present and most likely arose as consequence of the long-term colonization of the patient. The treatment probably induced a sudden decrease of population size, selecting a subpopulation, which acted as founder for the new population at T(1) characterized by a higher number of fixed mutations. These data demonstrate that genome plasticity is an important common prerequisite among gastric Helicobacter species for adaptation to the stomach environment allowing the bacterium to evolve rapidly once a selective pressure is applied.